In reply to Alun:
Double sessions are good.
For "day endurance" I would have one of the sessions as AeroCap. The best way I have found to train this are 20/10's.
-Sort out a 20 move circuit on your board just below onsight limit with all moves about the same difficulty. Do the circuit of 20 moves and then 20 seconds rest followed by 10 moves back of the circuit then 10 secs rest (30 moves). Do this four times back to back (120 moves)getting on back on the board each time at the point you left off so you end up doing the circuit in different ways (which an be confusing when you get tired !)
-Take 10 min rests between sets and aim for 3/4 sets in a session.